Pressure relief valve for a packaging container

ABSTRACT

A pressure relief valve ( 2 ) for a packaging container ( 1 ) includes a base plate ( 3 ), which can be fastened on a wall of the packaging container and has a valve opening ( 9 ). The valve ( 2 ) also includes a membrane ( 4 ) which is arranged on the base plate ( 3 ) over the valve opening ( 9 ), wherein the membrane ( 4 ) has an adhesive on one side. The valve ( 2 ) also includes an intermediate layer ( 6 ), which is adhesively bonded to the adhesive-containing side of the membrane such that the membrane ( 4 ) has two remaining, parallel adhesive-containing peripheral zones for fastening on the base plate ( 3 ). The membrane ( 4 ) is arranged on the base plate by way of the intermediate layer ( 6 ) such that a channel zone ( 14 ) is formed on the base plate ( 3 ). The channel zone covers over the valve opening ( 9 ) and rests right up against the base plate in the closed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/512,462, now U.S. Pat. No. 8,887,766, filed Aug. 8, 2012, which is a371 national phase application of PCT/EP2010/065685, filed Oct. 19,2010, which claims priority to DE 10 2009047170.7, filed Nov. 26, 2009,the entire contents of each of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a pressure relief valve for a packagingcontainer.

Oxygen-sensitive goods, like, for example, coffee, are packaged intightly sealed packaging containers in order to prevent spoilage due tooxygen. Because freshly roasted coffee does however produce carbondioxide, increased pressure would then build up, which swells andeventually bursts the package. It is therefore known to provide thepackaging container with pressure relief valves. A pressure reliefvalve, which comprises a base plate having a valve opening and amembrane over said valve opening, is known, for example, from theEuropean Parliament patent publication EP 0 760 790 B1. The valveopening is thereby configured from two intersecting, annular openings.This pressure relief valve has basically proven to be successful, hashowever relatively large dimensions. For that reason, the pressurerelief valves from prior art have to almost always be arranged on afront face. Front faces of this kind are however used as presentationsurfaces and therefore undesirable restrictions result, for example withregard to the printing on the packaging, by mounting the pressure reliefvalve on the front face. The known pressure relief valve is furthermorerelatively complex to produce because the base plate has to be partiallywetted with adhesive and the membrane then affixed to the base plate. Inso doing, a wrinkling can quickly occur, whereby the pressure reliefvalve is no longer leak-proof.

SUMMARY OF THE INVENTION

The inventive pressure relief valve has in contrast the advantage thatit can be very easily and cost effectively manufactured and particularlycan be manufactured with reduced dimensions. Besides a desirablematerial savings, the big advantage ensuing therefrom is that thepressure relief valve according to the invention can be arranged at anydesired position on the packaging container. For example, the inventivepressure relief valve can now also be arranged on narrow or back sidesor along the longitudinal seam of the packaging. According to theinvention, this is achieved as a result of the pressure relief valvehaving a base plate comprising a valve opening, a membrane and anintermediate layer. The membrane comprises one side, on which anadhesive coating has been completely applied, and the intermediate layeris bonded to the membrane by means of the adhesive coating such thatsaid membrane comprises two parallel peripheral zones for fastening onthe base plate. In other words, the adhesive coating of the membraneserves on the one hand to affix the intermediate layer and on the otherhand to fasten the membrane on the base plate. In so doing, the membraneis adhesively bonded to the base plate by way of the intermediate layersuch that a channel zone is formed, which provides an outlet channelthrough the valve opening when a positive pressure exists in theinterior of the packaging container, and the membrane rests right upagainst the base plate in the closed position. According to theinvention, the membrane can therefore simply be completely coated on oneside with an adhesive and a bonding of the membrane to the base platecan be prevented by the intermediate layer which is affixed to saidmembrane. In addition, a simple modular construction can thereby beachieved because by means of a simple variation of the thickness of theintermediate layer, an opening pressure, whereat the pressure reliefvalve opens, can be set. As a result, no further dimensions of thepressure relief valve have to be changed, but merely anotherintermediate layer having a different thickness has to be affixed.

It is particularly preferred for the intermediate layer to be adhesivelybonded to the center of the membrane. A symmetrical construction andeven opening characteristics of the pressure relief valve result therebyas well as two equally large peripheral zones for fastening on the baseplate. It is particularly preferred for the intermediate layer to have alarger thickness than the membrane. In so doing, a stiffening effect ofthe intermediate layer on the membrane can be achieved.

It is further preferred for a ratio of a surface area of theintermediate layer to a surface area of the valve opening to be selectedsuch that the equation 3 # V # 4 is satisfied, wherein V is preferablyapproximately 3.5. By adjusting this amount, it has surprisingly beenshown that excellent sealing and opening properties of the pressurerelief valve can be provided independently of an absolute size of thevalve opening or the channel zone.

The valve opening in the base plate has preferably a surface area, whichis less than 30 mm² and more preferably less than 25 mm². This ensures avery small overall dimension of the pressure relief valve.

The base plate has preferably a surface area, which is less than 250mm², more preferably less than 160 mm². It can thereby be ensured thatthe pressure relief valve can be mounted at any desirable position onthe packaging container.

The invention furthermore relates to a pressure relief valve comprisinga base plate which has a valve opening and a membrane and can be mountedon a wall of the packaging container. The membrane is arranged on thebase plate over the valve opening and fastened on the base plate bymeans of two parallel peripheral zones such that a channel zone isformed on said base plate which defines an outlet path when a positivepressure occurs and rests right up against the membrane in the closedposition. A ratio of a surface area of the channel zone to a surfacearea of the valve opening is thereby selected such that the equation 3 #V # 4 is satisfied, wherein the ratio of the surface areas of thechannel zone to the valve opening is preferably approximately 3.5. Byadhering to these dimensions of the surface areas of the channel zone tothe surface area of the valve opening, a reliable opening of thepressure relief valve can be ensured for every pressure range. It wasfurthermore surprisingly determined that a significant reduction in thedimensions of the pressure relief valve is possible when there isadherence to these dimensions. The adherence to these dimensions furtherensures that favorable lever ratios are achieved between the membraneand the valve opening, whereby the vacuum resistance is also increased.Because of this fact, it is possible for the first time for theinventive pressure relief valve to also fulfill the requirements of thecan industry for containers.

The valve opening is especially preferably formed by two intersectingcircular surfaces, preferably having the same radius. A simple geometricconstruction is thereby achieved, wherein two inwardly directed cavityapexes result at the valve opening.

A longitudinal extension of the valve opening equal to one half of alength of the base plate is further preferred. The opening properties ofthe pressure relief valve can thereby be even more improved.

According to a further preferred embodiment of the invention, the valveopening formed by three or four or six intersecting circular sections.As a result, three cavity apexes ensue from three intersecting circularsurfaces, four cavity apexes from four intersecting circular surfacesand six cavity apexes from six intersecting circular surfaces. Theintersecting circular surfaces are preferably arranged such thatsymmetrical forms result.

A particularly good opening property results if the cavity apexespreferably have a triangular shape.

The pressure relief valve preferably further comprises a spacer, whichensures that the membrane can arch if a positive pressure occurs in thepackaging container. The positive pressure can thus be let out of thepackaging container.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred exemplary embodiments of the invention are described below indetail with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a schematic, perspective view of a packaging containercomprising a pressure relief valve according to a first exemplaryembodiment of the invention,

FIG. 2 shows an exploded view of the pressure relief valve of the firstexemplary embodiment,

FIG. 3 shows a top view of the pressure relief valve of the firstexemplary embodiment,

FIG. 4 shows a top view of the pressure relief valve according to asecond exemplary embodiment of the invention,

FIG. 5 shows a top view of a pressure relief valve according to a thirdexemplary embodiment of the invention,

FIG. 6 shows a top view of the pressure relief valve according to afourth exemplary embodiment of the invention, and

FIG. 7 shows a top view of the pressure relief valve according to afifth exemplary embodiment of the invention.

DETAILED DESCRIPTION

A pressure relief valve 2 according to a first exemplary embodiment ofthe invention is described below in detail with reference to the FIGS. 1to 3.

As can be seen in FIGS. 2 and 3, the pressure relief valve 2 comprises abase plate 3, in which a valve opening 9 is centrally arranged. The baseplate 3 has a square shape with rounded corners. The pressure reliefvalve further comprises a membrane 4, an intermediate layer 6 and afirst and a second spacer 7, 8. An adhesive coating 5 is applied to oneside of the membrane 4 and covers the entire side thereof. The externalshape of said membrane 4 thereby corresponds to the external shape ofthe base plate 3. The intermediate layer 6 is adhesively bonded to theadhesive-containing side of said membrane 4.

Two peripheral zones result thereby, which are parallel to one anotherand with which said membrane is adhesively bonded to the base plate 3.In so doing, the intermediate layer 6 covers the valve opening 9 as wellas a region on the base plate 3 situated in the longitudinal directionof the pressure relief valve. Said region is also referred to as channelzone 14. The channel zone 14 thereby has a length L1 and a width B2. Thewidth of the base plate 3 is denoted with B1, wherein B1 is equal to L1because said base plate is square. The channel zone 14 is therebyprovided in the direction of a longitudinal extension of the valveopening 9 and completely covers said valve opening 9.

As can be seen in FIG. 3, the valve opening 9 is formed from twointersecting circular surfaces 10, 11. The centers M1 and M2 of the twocircular surfaces 10, 11 thereby lie on a common axis X-X, which is alsothe center axis of the pressure relief valve 2. A first cavity apex 12and a second cavity apex 13 are furthermore formed at the valve opening9. The cavity apexes are thereby inwardly directed, wherein said cavityapexes 12, 13 are arranged in the longitudinal direction of the pressurerelief valve in the middle of the same. The two circular surfaces 10, 11have in each case the same radius R1 or R2. The surface area of thevalve opening 9 is approximately 23.28 mm².

The surface area of the intermediate layer 6 is B2×L1=78.13 mm². Theratio V of the surface area of the intermediate layer to the surfacearea of the valve opening 9 is therefore:V=78.13: 23.28=3.36.

The pressure relief valve 2 is thereby configured symmetrically aboutthe central axis X-X as well as about another central axis perpendicularthereto. The reference numerals 7 and 8 thereby denote a first and asecond spacer, which are adhesively bonded to the side of the membrane.The spacers 7, 8 ensure that the membrane 4 can arch in the region ofthe channel zone 14 when a positive pressure occurs in the interior of apackaging container.

FIG. 1 shows an exemplary application of the pressure relief valve 2according to the invention, which in the case of a packaging container 1is arranged at a base or head region and in the side gusset region ofthe head and the base. All lateral regions without regard to thepressure relief valve are available for printing, and thereforeadvertising and the like can correspondingly be printed thereupon.

It should be further noted that the intermediate layer 6 has a thicknessD2, which is greater than a thickness D1 of the membrane 4. Thestiffness of the membrane 4 and hence the opening behavior of thepressure relief valve 2 can be influenced by means of the selection ofthe thickness of the intermediate layer 6. The opening behavior of thepressure relief valve can thus be changed through a simple exchange ofthe intermediate layer 6 for an intermediate layer having anotherthickness. A modular construction can thereby be achieved in a simplemanner, and a large number of identical parts are retained for differentapplications of pressure relief valves, wherein merely differentintermediate layers 6 have to be available. Because the intermediatelayers 6 can be simply applied to the adhesive coating of the membrane 4by means of adhesive bonding, a simple and cost effectivemanufacturability of the pressure relief valve 2 can be achieved.

A miniaturization of the dimensions of the pressure relief valve 9 canfurther be achieved by the selection of the surface area ratios Vbetween the surface area of the intermediate layer 6 and the surfacearea of the valve opening 9 without negatively affecting the openingbehavior. A length L1 as well as a width B1 of the base plate 3 is 12.5mm in this exemplary embodiment. The inventive pressure relief valve canthus be arranged inconspicuously at any desirable position on apackaging container.

A pressure relief valve pursuant to a second exemplary embodiment of theinvention is described below in detail with reference to FIG. 4, whereinidentical or functionally identical parts are denoted with the samereference numerals as in the first exemplary embodiment. In contrast tothe first exemplary embodiment, the second exemplary embodimentcomprises a first cavity apex 22 and a second cavity apex 23, which areformed differently than in the first exemplary embodiment. In the caseof the second exemplary embodiment, the cavity apexes 22, 23 areconfigured in a triangular shape. In so doing, the cavity apexes extendfurther in the direction of a center M of the valve opening 9. A fasteropening behavior of the pressure relief valve 2 is achieved by thischange, i.e. the pressure relief valve 2 of the second exemplaryembodiment already opens at a smaller positive pressure than that of thefirst exemplary embodiment. Otherwise this exemplary embodimentcorresponds to the preceding exemplary embodiment, and thereforereference can be made to the description provided there.

FIGS. 5 and 6 depict a third and fourth exemplary embodiment of theinvention. In this case, the valve opening 9 is formed from fourintersecting circular surfaces. Four cavity apexes 31, 32, 33, 34 ensueas a result. The third exemplary embodiment of FIG. 5 thereby has cavityapexes which result from the intersecting circular surfaces. The fourthexemplary embodiment has in this connection two cavity apexes 35, 36which have a triangular shape.

FIG. 7 depicts a fifth exemplary embodiment of the invention, whichcomprises a valve opening 9 that is formed from six intersectingcircular sections. Six cavity apexes 41, 42, 43, 44, 45, 46 therebyresult. By means of these six inwardly directed cavity apexes of thevalve opening 9, a very sensitive pressure relief valve 2 can beachieved, which opens already at small positive pressures of just a fewpascals. Otherwise this exemplary embodiment corresponds to thepreceding exemplary embodiments, and therefore reference can be made tothe description provided there.

What is claimed is:
 1. A pressure relief valve for a packaging containercomprising: a base plate (3) configured to be fastened on a wall of thepackaging container and having a valve opening (9); a membrane (4) whichis arranged on the base plate (3) over the valve opening (9), whereinthe membrane (4) has an adhesive on one side; and an intermediate layer(6) which is adhesively bonded to the side of the membrane (4) that hasthe adhesive, such that the membrane (4) has two remaining edge zoneswhich have adhesive for fastening to the base plate (3); wherein themembrane (4), in conjunction with the intermediate layer (6), arearranged on the base plate (3) in such a way that a channel zone (14) isformed on the base plate (3), wherein the intermediate layer (6) coversthe valve opening (9) and rests up against the base plate (3) in aclosed position, wherein a ratio (V) of an area of the intermediatelayer (6) to an area of the valve opening (9) satisfies the equation3≦V≦4, and wherein the valve opening (9) is formed from one of a groupconsisting of three, four, and six intersecting circular areas.
 2. Thepressure relief valve according to claim 1, wherein the intermediatelayer (6) is adhesively bonded to a center of the membrane (4).
 3. Thepressure relief valve according to claim 1, wherein the intermediatelayer (6) has a width (B2) which is approximately one half of a length(L1) of said intermediate layer (6).
 4. The pressure relief valveaccording to claim 1, wherein the valve opening (9) has a surface areawhich is equal to or less than 30 mm².
 5. The pressure relief valveaccording to claim 1, wherein a longitudinal extension (L2) of the valveopening (9) is equal to one half of a length (L1) of the base plate (3).6. The pressure relief valve according to claim 1, wherein the valveopening (9) has multiple cavity apexes (31, 32, 33, 34, 35, 36).
 7. Thepressure relief valve according to claim 6, wherein the valve opening(9) has four cavity apexes (31, 32, 33, 34).
 8. The pressure reliefvalve according to claim 6, wherein the cavity apexes (35, 36) aretriangular in shape.
 9. The pressure relief valve according to claim 1,wherein V is approximately 3.5.
 10. The pressure relief valve accordingto claim 1, wherein the valve opening (9) has a surface area which isless than or equal to 25 mm².
 11. The pressure relief valve according toclaim 1, wherein the valve opening is formed from intersecting circularsurfaces having the same radius.
 12. The pressure relief valve accordingto claim 1, wherein the valve opening (9) is formed from threeintersecting circular surfaces.
 13. The pressure relief valve accordingto claim 1, wherein the valve opening (9) is formed from fourintersecting circular surfaces.
 14. The pressure relief valve accordingto claim 1, wherein the valve opening (9) is formed from sixintersecting circular surfaces.
 15. The pressure relief valve accordingto claim 1, wherein when a pressure inside a container is at or abovethe predetermined pressure, the membrane (4) arches in the channel zone(14) over the valve opening (9) and the base plate (3) to allow pressureto be let out of the container.
 16. The pressure relief valve accordingto claim 1, wherein the edge zones are parallel.
 17. The pressure reliefvalve according to claim 1, wherein the edge zones are disposed onopposite sides of the intermediate layer.
 18. The pressure relief valveaccording to claim 1, wherein the intermediate layer is disposed betweenthe base plate (3) and the membrane (4).
 19. The pressure relief valveaccording to claim 1, wherein the intermediate layer directly contactsthe base plate (3) and covers the valve opening (9) when a pressureinside a container is below a predetermined pressure.
 20. The pressurerelief valve according to claim 1, wherein the membrane (4) has anadhesive on a side facing the base plate (3).